It should be the norm across industries. I don't know if this is done or not in retail, but it is common enough in manufacturing (even in non-union shops). It event has a name; it's called a shift differential, and it can be quite lucrative for the employee. Especially if they can work a normal 40-hour week and pick up a night shift on Saturday or Sunday. That one additional shift, with the shift differential and overtime could be the equivalent of two and a half or three normal days.